Rotor of electric rotating machine

Abstract

A rotor of alternator has core layer units serially located along axial direction. Each unit has a field coil generating magnetic flux and two rotor cores receiving the flux on respective sides of the coil in axial direction. Each core has a first yoke portion located on inner side of the coil, a second yoke portion extending from the first yoke portion toward the outer side and magnetic poles extending from the second yoke portion in the axial direction. The poles of one core and the poles of the other core in each unit extend toward different axial sides and are alternately arranged in circumferential direction on the outer side of the coil. A ratio of the outer circumferential diameter of the first yoke portions to the rotational diameter of the poles is lower than 0.54.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is based upon and claims the benefit of priority of the prior Japanese Patent Application 2010-76652 filed on Mar. 30, 2010, so that the contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a rotor of an electric rotating machine such as an alternator for a vehicle.[0004]2. Description of Related Art[0005]An alternator mounted on a vehicle has a cylindrically-shaped stator and a rotor located in the center space of the stator. FIG. 1 is a side view, partially in cross section, of a rotor of an alternator according to a prior art. As shown in FIG. 1, a rotor 100 of an alternator has a rotational shaft 104 revolving on its shaft center, a single core layer 102 rotated on its central axis with the shaft 104, slip rings 106 through which electric current flows to the core layer 102, and fans 107 located on respective sides of the...

AI Technical Summary

Benefits of technology

[0014]An object of the present invention is to provide, with due consideration to the drawbacks of the conventional alternator, a rotor of an electric rotating machine which is lightened in weight so as to increase electric power generated per unit weight of the machine or rotational force generated per unit weight.

[0017]In this case, as compared with a conventional rotor having a single field coil and two rotor cores placing the coil between the cores, the number of turns in each field coil generating one of the distributed magnetic fluxes can be reduced so as to lighten the total weight of the field coils.

[0018]Further, because the core layer units are serially located along the axial direction, the length of each core layer unit in the axial direction is shortened, as compared with the conventional rotor. In this case, because the cores are necessarily thinned in the axial direction, the path of the magnetic flux passing through the cores while surrounding the field coil is shortened so as to reduce magnetic reluctance or resistance caused in the cores, and the difference in the path lengths of magnetic force lines in the cores is reduced so as to uniformly set the density of the magnetic flux in the cores. Therefore, the magnetic flux density can be heightened.

[0019]Accordingly, the rotor can be lightened in weight or can increase the magnetic flux density so as to increase the electric power or the rotational force generated per unit weight in the machine.

Problems solved by technology

However, the weight of the alternator disclosed in the Publication (No. 2008-054392) is undesirably increased by the magnets, and it is required to stably fix the magnets in the rotor.

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